Heating the bottle
How much your baby will want to feed will vary, and the spacings between feeds can range from 1 to 2 hours, to 4 to 6 hours in a 24 hour period. Newborn babies initially need to feed frequently for nourishment, and their instinctual needs are the main reason they will wake frequently overnight, especially in the first couple of months. Babies also need to adjust to digesting their food, and can sometimes take a few days to 'adjust' to drinking formula.
It is generally recommended that bottle fed babies (at least up to 3 to 4 months old) be fed 'on demand', rather than a structured feeding pattern, determined by the parents. 'Stretching out' the time between feeds, especially in the early weeks can distress the baby, usually equating to an unhappy and unsettled baby. Your baby wakes for nourishment and their stomachs are small, therefore only meant to tolerate small, regular feeds. By the time the baby is 8 to 12 weeks old, they will most likely move into a more 'adult friendly' sleep pattern (although this is not guaranteed).
Some babies will drink their bottle quite quickly (within 10 to 15 minutes or so), others may take their time feeding, occasionally pulling off the teat to rest (up to 30 to 40 minutes). On average, it will take you about 30 to 50 minutes to feed and burp your baby. Be aware that if the milk flow is too fast for them, they may want to suck more after the feed to feel content. (The sucking time helps to settle and soothe your baby.) Also if the milk flow is too slow, they may tire before they have actually finished a feed, meaning they will not settle for as long in between feeds before waking up hungry again. Premature babies often tire more quickly and may need to have a faster flowing teat.
To test the milk flow, when you hold the bottle upside down, the milk should drip out at a steady rate.